Method of treating wool and fabrics formed therefrom to increase their resistance to decomposition by heat



Patented July 18, 1950 IWETHOD OF TREATING WOOL AND FABRICS FORMEDTHEREFROM TO INCREASE THEIR RESISTANCE TO DECOMPOSITION BY HEAT CharlesR. Barnes, Pittsburgh, Pa., assignor to Albany Felt Company, Albany, N.Y., a corporation of New York No Drawing. Application April 13, 1948,

Serial No. 20,848

15 Claims.

Many fabrics formed entirely or in substantial part of wool fibers areused in the mechanical arts for purposes where they are subjected toelevated temperatures. For example, fabrics used for filteringchemicals, or as slasher cloth for applying sizing material to yarns orfabrics, are often subjected totemperatures near the boiling point ofwater Fume bags are used for collecting dust from air at temperaturesoften as high as 250 to 300 F. Some fabrics are used for filtering oilsat temperatures as high as 350 F., while others are used for applyingparaffin coatings at high temperatures to milk bottle caps, paperboardcontainers, and the like. Blankets, such as Sanforizing blankets, whichare used in shrinking other fabrics, are also subjected to comparativelyhigh temperatures While in a moist condition. Thus, many wool fabricsare subjected both to dry heat and to heat while wet or moistened withvarious liquid media.

Wool fibers when subjected to temperatures of the above order decomposequite rapidly, depending upon temperature and other conditions, with theresult that the life of the fabrics formed therefrom is comparativelyshort.

Therefore, the principal object of my invention is to provide acomparatively simple treatment whereby the resistance to heat of woolfabrics formed therefrom is substantially increased. It is to beunderstood that my invention is not limited in its application tofabrics formed entire- 1y of wool, because it may be applied to fabricsformed in part of wool and other fibers, such as cotton, rayon, nylonand the like, for increasing the resistance to heat of the Wool contentthereof. a The wool may be processed at almost any stage of itsfabrication into a textile. Thus, the treatment may be applied to the.scoured raw Wool, to the yarn, or to the fabric after it is formed. Iprefer, however, to treat the Woven fabric since it is most convenientto process the Wool when in this form.

I have discovered that the heat resistance of W001 is improved to agreater or lesser extent by treatment in water solution with the complexthiocyanate ions ofsuch metals as form complex metallo-thiocyanate ionsin the solution. Those thiocyanates which form the more symmetricalthiocyanate complex ions are more effective than those which formcomplex ions of the asymmetricaltype. The general type of themetallothiocyanate complex ions may be represented by the formula[MfSCNMR in which M is a metal, 11 the number of thiocyanate groupscontained by the ion, and e the quantity of negative charge upon theion. The value of e is found by subtracting n from the valence of themetal. When the numerical value of e'is an even number, a

more symmetricaltype of thiocyanate complex.

ion is formed than when 6 is odd, For instance, zinc or cadmiumthiocyanates in water solution.v

form symmetrical complex ions which may be represented in the case ofthe zinc salt as followsz Examples of the asymmetrical type of complex.ions are those formed by ferric, aluminum or,

chromium thiocyanates which may be represent: ed in the case of theferric salt as follows:

Such negatively charged complex ions evidently form metallo-thiocyanatecross linkages between the polypeptide chains at positive groups in thewool, thus producing a modified wool which is more resistant todecomposition by heat.

The effectiveness of the thiocyanate complex also depends on the radiusof the ion, its solubility, and its stability as well as the stabilityof the metallo-thiocyanate complex formed With the Wool. For instancethe symmetrical zinc thiocy anate complex ion apparently has the optimumdiameter to produce the most effective metallothiocyanate-wool complex.Cadmium whose ions are larger than those of zinc is slightly lesseffective, and, consequently, all other metalsv of greater atomicdiameter than zinc are much less effective. v

Regarding those metals whose atomic radii are less than that of zinc andwhich are capable of forming stable symmetrical thiocyanate complex:

ions in water solution, I have found that cupric thiocyanate is quiteeffective in protecting Wool against the action of wet heat but lesseffective against the action of dry heat, where, apparently,

the wool-cupric thiocyanate complex decomposes at elevated temperatures.Likewise, beryllium, whose ions are much smaller than those of zinc,also forms a metallo-thiocyanate-wool complex which is quite effectiveagainst decomposition by wet heat but less effective against the actionof dry heat.

Evidence, including X-ray diffraction patterns;

indicates that the metal thiocyanate forms a cross-linkage at the aminogroups of the Wool thus leaving the disulfide linkagesintact. In

other words, the thiocyanate chemically combines withthe Wool to formtherewith an organic,

metallo-thiocyanate complex.

In practice, the fabric to be treated may be thoroughly wet, thechemicals are added to the water in the same way that dyes are normallyadded in the dyeing of fabrics. That-is to say, they are added graduallyover a period of perhaps 10 to 30 minutes and at a rate which is adaptedtocient time to become thoroughly saturated and to react with thechemical in the solution. At 115 F., satisfactory saturation may beeffected in about two hours. After the treatment, the

fabric is extracted, dried, and finished in the normal way.

Instead of treating the woven fabric. thewool, I

as pointed out above, may be treated after it is secured, or after ithas been made into yarn. This can be done in a number of ways, but theimportant features to be observed in all cases are that the materialtreated is brought into intimate contact with the treating solution, andthat some relative motion between the wool and the solution take placeduring the treatment.

The temperature of the solution is not critical because the treatmentmay be carried out with the solution at room temperatures or attemperatures considerablyhigher than the range mentioned above. At lowertemperatures a longer time is required in order to effect an equivalentdegree of treatment and, at higher temperatures, less time is requiredbut, if the temperature is too some deterioration of the fabric mayresult therefrom. The temperature range of 115 to 120 F., is preferredbecause it allows practical speed without appreciable adverse effect onthe fabric. The quantity of chemical necessary to improve the heatresistance of the wool varies over a .considerable range depending onthe temperatures at which the treatment is conducted, the durationtherefrom, etc. A solution containing, by weight, as little as 0.07% hassome beneficial efi'ect, and as much as 20% or more may be used.However, from 1 to- 3% is sufficient to treat the-wool effectiyely whenapplied for two hours at 115 and is therefore preferred in the practicalapplica-. tion of my process.

, The tests set forth in Tables I and II below indicate that theforegoing treatment makes the fabric substantially more resistant toboth wet and dry heat than an untreated fabric.

1. Alibi the above samples were submerged in distilled water for 6 hoursat 209 F. before they were tested.

2. The percent of the chemicals refers to that of the metal thiocyanatecalculated stoichiometrically from the salts indicated. 7

Table II T 1 Tensile Per Cent Treatment Strength, improve- 11 Poundsment 65. 2 0 1% (ZDACZd'NH4SCN) 67. 8 4. 0 0 (ZnACz-I-NH4SCN)-.- 78. 219. 9 1 0% (ZILACB+NH4SON) 87. 0 33. 4 2 0% (ZHAO2+NH4SCN 94. 6 45. 1 0%(Zl'lACz-I-N HtSCN 100. 2 53. 7 10 0% (ZD.A(!2+NH4SCN) 98. 5 51. 1 0%(ClCzOi-i-NHtSCN) 68. 5 5. 1 (.QdClz-f-NHASCN) s 85. 6 31. 3(NlO1O4-l-NH4SCN) 66. 9 2. 6 ohm) s1. 2 24. 5 (CdGlz-l-NHaSCN) 79. 3 21.8 1% (ZHCI +NH4SCN 78. 8 21. 0 O 07% (CdC12-1-NH4SCN 66. O 1. 0 0 07%(ZnClz-I-HN4S ON) 65. 3 0. 0 (OdG1z-i-NH4SGN) 88. 5 36 20%(ZnC12+NH4SCNX; 108. 8 67 Norms 1. All of the above tests were subjectedto dry heat at 284 F. for 24hcurs before they were tested. 2. Thepercent of the chemicals refers to that of the metal thiocyanatecalculated from the salts indicated stoichiometrically.

Other tests, in which specimens of treated and untreated Wool weresubjected to dry heat at 284 for 24 hours, the'gases given 01f by thewool collected by continually sweeping them from Per'Cent Per CentTreatment Sulfur Ammonia Lost Lost None 0. 0095 0. 0569 2% ZIKSGN )20.0083 0. 0140 'X-ray diffraction patterns indicate that there is nochange in the side chain spacing between the treated and untreated woolin either the slack condition or when stretched This would indicate thatthe treating chemicals have been added to the amino groups rather thanbreaking the disulfide bonds.

As pointed out'above, the preferred metal salts are the zinc and cadmiumthiocyanates. It is not necessary that these salts be added as such tothe water but only that the thiocyanate ions and the metal ions bepresent in the same solution. This, ammonium thiocyanate with zincchloride or other zinc salt giving the zinc ion is equally effective.

Water solutions of'metal thiocyanates. other than those of zinc andcadmium have been found helpful in enhancing the resistance of woolfibers to decomposition when heated, but the thiocyanates of zinc andcadmium are definitely superior to the others, and hence, are preferred.

What I claim is:

I. A fabric formed substantially of wool fibers and characterized by itsresistance to decomposition when subjected to temperatures up to about300 F.; said fabric having a complex, metallothiocyanate chemicallycombined with said fibers but being otherwise substantially free ofother metallic compounds.

2. A fabric formed substantially of wool fibers and characterized by itsresistance to decomposition when subjected to temperatures up to about300 F.; said fabric having a metal capable of formin symmetrical complexions with thiocyanates in water solution chemically combined with saidfibers, out being otherwise substantially free of other metalliccompounds.

3. The fabric set forth in claim 1 in which the metal forming saidcomplex, metallo-thiocyanate 1s Zll'lC.

4. The fabric set forth in claim 1 in'which the metal forming saidcomplex, metallo-thiocyanate is cadmium.

5. A fabric formed substantially of wool fibers and characterized by itsresistance to decomposition when subjected to temperatures up to about300 F.; in the presence of moisture; said fabric having a complex,cupric-thiocyanate chemically combined with said fibers but beingotherwise substantially free of other metallic compounds.

6. The method of increasing the resistance of wool to decomposition whenexposed to tempera tures up to about 300 R, which consists in treatingsaid wool in a water solution containing metal ions and thiocyanate ionsuntil the fibers of said wool are thoroughly saturated with saidsolution and an organic, metallo-thiocyanate complex is formedtherewith; and thereafter drying said wool.

7. The method of increasing the resistance of a textile fabric formedsubstantially of wool fibers to decomposition when subjected totemperatures up to about 300 R, which consists in treating said fabricin a water solution containing at least 0.07%, by weight, of a metalthiocyanate until said fibers are thoroughly saturated with saidsolution, and an organic, metallo-thiocyanate complex is formedtherewith; and thereafter drying said fabric.

0. The method set forth in claim 7 in which the metal forming said metalthiocyanate is a metal capable of forming a symmetrical, thiocyanate,complex ion.

9. The method set forth in claim 7 in which the metal forming said metalthiocyanate is zinc.

10. The method set forth in claim 7 in which the metal forming saidmetal thiocyanate is cadmi-um.

11. The method set forth in claim 7 in which the metal forming saidmetal thiocyanate is copper.

12. The method set forth in claim 7 in which the quantity of metalthiocyanate in said solution is from about 1% to about 3%, by weight.

13. The method set forth in claim 7 in which the temperature of saidsolution is maintained in the approximate range of to F., and the metalforming said thiocyanate is zinc.

14. The method set forth in claim 7 in which the temperature of saidsolution is maintained in the approximate range of 115 to 120 F., andthe metal forming said thiocyanate is cadmium.

15. The method set forth in claim 7 in which the temperature of saidsolution is maintained in the approximate range of 115 to 120 F., andthe metal forming said thiocyanate is copper.

CHARLES R. BARNES.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,757,519 Ellis May 6, 19301,947,024 Slagle Feb. 13, 1934 2,028,769 Ellis e Jan. 28, 1936

1. A FABRIC FORMED SUBSTANTIALLY OF WOOL FIBERS AND CHARACTERIZED BY ITSRESISTANCE TO DECOMPOSITION WHEN SUBJECTED TO TEMPERATURES UP TO ABOUT300*F.; SAID FABRIC HAVING A COMPLEX, METALLOTHIOCYANATE CHEMICALLYCOMBINED WITH SAID FIBERS BUT BEING OTHERWISE SUBSTANTIALLY FREE OFOTHER METALLIC COMPOUNDS.